Motor starting winding switch



July 11, 1961 HEDQUIST ETAL 2,992,305

MOTOR STARTING WINDING SWITCH Filed July 29, 1958 wire INVENTORS. ALBERTJ /-/E0c2u/sr- I MITCHELL ATTDRN EYS Patented July 11, 1961 2,992,305MOTOR STARTING WINDING SWITCH Albert J. Hedquist, Ferry Road, NewBrunswick, Canada, and Leo A. Mitchell, Newcastle, New Brunswick, CanadaFiled July 29, 1958, Ser. No. 751,696 3 Claims. (Cl. 200-87) Thisinvention relates to electric motors, and more par ticularly to astarter for an electric motor.

The object of the invention is to provide a cutout switch for anelectric motor such as a split phase motor, and wherein according to thepresent invention a magnetic field obtained from the motor current isused.

Another object of the invention is to provide an electric motor startingswitch which can be mounted either on the inside or the outside of themotor and wherein the device has no attachment to the rotor, the presentinvention being adaptable to any size of split phase motor and whereinthe device is easy to install and requires no service or adjustment.

A still further object of the invention is to provide a motor attachmentwhich utilizes the motor current and a magnetic field for the desiredswitching action.

A further object of the invention is to provide an electric motorstarter which is extremely simple and inexpensive to-manufacture.

Other objects and advantages will be apparent during the course of thefollowing description.

In the accompanying drawings, forming a part of this application, and inwhich like numerals are used to designate like parts throughout thesame:

FIGURE 1 is an end elevational view illustrating the electric motorstarter of the present invention, and showing the motor shaft insection.

FIGURE 2 is a side elevational view of the device of FIGURE 1.

FIGURE 3 is a plan view of the assembly of FIG- URES 1 and 2.

FIGURE 4 is a wiring diagram illustrating the present invention.

Referring in detail to the drawings, the numeral indicates the electricmotor starter of the present invention, and it will be seen that themotor starter or switch 10 includes a center support member or disk 11which is provided with a central opening 12 through which may extend ashaft such as the motor shaft 13, FIGURES 1 and 2.

Extending from the support member 11 and connected thereto is aplurality of spaced apart brackets 14. The numerals 15, 16 and 17indicate wires or conductors, while the numeral 18 indicates a coilwhich has a core arranged therein.

The numeral 20 indicates a stationary base which is secured to the core19 in any suitable manner, and a pair of spaced apart contacts or points21 are connected to the base 20. The numeral 22 indicates a movablearmature which has one end pivotally or hingedly connected to the core19 as at 23. The other end portion of the armature 22 is mounted formovement into and out of engagement with an end 24 of the stationarycore 19.

Mounted below the armature 22 is an insulated strip 25, and arrangedbelow the strip 25 and connected to the armature 22 is a terminal orcontactor 26. The terminal 26 is mounted for movement into and out ofelectrical engagement with the contacts 21.

Extending from an end of the armature 22 and connected thereto orsecured thereto in any suitable manner is an car 27, and the numeral 23indicates a resilient means or coil spring which is connected to the car27. A securing element such as a bolt 29 extends outwardly from the core19, and a nut 30 is arranged in threaded engagement with the securingelement 29. The numeral 31 indicates a clamp which is provided with aslot 32, and the slot 32' has the securing element 29 extendingtherethrough. The provision of the slot 32 permits the nut 30 to beloosened so that the clamp 31 can be moved to different adjustedpositions, and then the nut 30 can be tightened so that the tension ofthe coil spring 28 can be varied or regulated as desired.

Referring to FIGURE 4 of the drawings, there is illustratedschematically the wiring diagram for the present invention, and it willbe seen that numeral 33 indicates a conventional motor which includesthe usual windings 34 and 35. The numeral 36 indicates power input orpower supply lines which may have a suitable switch 37 connectedthereto.

From the foregoing, it is apparent that there has been provided a devicewhich is especially suitable for starting electric motors such as thesplit phase type, and wherein there is utilized a magnetic fieldobtained from the motor current.

It is known that a split single phase motor when starting will draw fromthree to four times as much current as when it has gained its normalspeed. According to the present invention this current is utilized toclose a switch which is connected in series with a starting winding suchas the winding 35 in the motor 33. The heavy starting current produces amagnetic field which closes the switch by moving the armature 22 againstthe tension of the spring 28 so as to energize the starting windingwhereby the motor starts and gains speed. As the motor approaches normalspeed, the current drops, so as to weaken the magnetic field. Then, thetension of the spring 28 opens the switch so as to cut the startingwinding out of the circuit. There is a great margin of magneticattraction between the starting and running which permits the spring 28to break contact. It is believed obvious that this is the proper way ofgetting control, rather than depending on centrifugal force to open theswitch which is the conventional way, where a switch is mounted on theinside of an end bell and the prior devices are very complicated and aremounted on the rotor and spin with the rotor which has a tendency toblock or fly apart or fail to reach the switch or fail to withdraw fromthe same which often results in burned out windings or the like.

The present invention can be mounted from the inside or outside on theend bell and it has no attachment to the rotor, and it will fit any sizesplit phase motor and is very simple and cheap to manufacture and isalso easy to install and requires no service or adjustment. A main pointof the present invention is that the motor current is utilized as wellas a magnetic field for the desired switching.

The terminals 26 are insulated from the armature 22 by means of theinsulated strip 25, and these terminals 26 are arranged so that theywill be properly aligned with respect to the contacts 21. The contacts21 are insulated from each other. The armature 22 does not carry currentand as previously described, the slot 32 permits the tension on thespring 28 to be adjusted or regulated as desired.

When the line switch 37 is closed, the rush of motor current through therunning winding 34 and also through the series coil 18 is many times thevalue of the normal run. The magnetic attraction overcomes the springtension 28 to thereby close the terminals 26 on the contacts 21 whichcompletes the circuit for the starting winding 35. As the motor gainsspeed, the current diminishes so that the coil 18 gets weaker andfinally the spring 28 overcomes the attraction of the coil 18 to therebycut or move the starting winding out of the circuit as is the 3practice. With the prior devices or earlier systems the cutout switchhad to be mounted within the motor which is dangerous in certainlocations due to sparking at the points. With the present invention thecutout switch it can be mounted at a great distance from the motor or itcan be mounted from within the motor.

The device can be used on split phase motors of different sizes orhorsepower and the only requirement is an initial adjustment for eachsize motor. The unit can be mounted inside or outside the motor withsuitable clamps and when mounted inside, the rotor shaft 13 extendsthrough the unit which is clamped to the end bell. This conserves spacewhich is very important and it can be used on existing motor without anychange.

Furthermore, the instant starting effort of a motor when using thepresent invention is from 30% to 50% greater with or without startingcapacitors. This is believed due to the slight time delay of currentthrough the action of the switch for the starting winding which is ahighly advantageous factor or point.

In motors such as fractional horsepower electric motors, there is a typewhich is called a split phase squirrel cage motor, and the rotor of thistype of motor would resemble a squirrel cage if all of the iron wasremoved, with copper bars and end rings exposed. Such motors have twowindings in the motor field, one of which is called the running windingwhich is the only winding used after the motor has gained its speed. Amotor of this: type with only the running winding is not able to startfrom rest so that a second winding is found in this motor field which iscalled the starting winding. This winding is placed in such a way in themotor field that it splits the single phase and creates a startingtorque and when the motor is up to speed, this winding is not needed,therefore, it is cut out of the circuit by a centrifugal switch which isin series with the starting winding. Switch points are generally mountedon the inside of the end bell and 'a mechanical device is mounted on therotor shaft which is operated by centrifugal force so that this is oftenreferred to as a centrifugal switch. The present invention will take theplace of the centrifugal switch so that it will be seen that in effectthe present invention is a starting winding switch for split phasemotors utilizing motor current and magnetic field for operation.

The mounting adaptor 11 can be made of a suitable of the series coil 18are common. The other point 21 has a lead 15 connected to it. At theother end of the coil 18 is the lead 17. The leads 15, 16 and 17 aremade to reach motor terminals when mounted on the inside or outside ofthe motor.

The contactor 26 completes the circuit through the points 21 whenattracted by action of motor current through the series coil 18.

material such as Bakelite, plastic, fiber board, or a suitableinsulating material to which the unit is secured by metal brackets 14,or by any suitable attaching means. The core 19 is adapted to be madefrom a suitable material such as laminated steel such as that type whichis used for small transformers, AC. motors or relays, and is curved to asemi-circle or horseshoe shape and riveted together; The end 23 of thecore is is extended and bent and is provided with a slot to receive thearmature 22 to serve as a hinge and a pivot may be used. The base Zll ismade from: a nonmagnetic, non-conductive material which does not conductelectric current. When armature 22. is opened by tension of the spring28, the air gap should not be too great and should be just sufiicient tobreak contact between the fingers 26 and points 21. The finger contacts25 are split at one end but are electrically one, and the split servesto give better alignment with the contact points 21, which the members26 are bridging when closed. The members 26 are electrically insulatedfrom the armature 22 at the anchorage, and the strip 25 is extended toprevent accidental contact with the free end when being attracted to theend portion 24 by the magnetic field. The electrical circuit is entirelyinsulated from the magnetic circuit.

As indicated by the showing in FIGURE 4, the ends of the lines or wiresare brought out to a terminal box on the motor. The lead 16 and point21, and one end When the line switch 37 is open, the armature is heldopen by tension of the spring 28. When the line switch 37 is closed, arush of current through the lead 16 which is connected to one end of theseries coil 18, from which it flows through lead 17 to motor runningwinding 34 and back to line switch 37. The rush of current throughrnember 18 magnetizes the core 19 which attracts armature 22 toward thepole piece 24 and in so doing the contactor 26 closes the circuitthrough points 21 to lead 15, through starting winding 35 back to switch37 which completes the circuit through the starting winding and motor sothat the motor will start; as the motor approaches full speed thecurrent drops to normal in running winding which is in series with thecoil 18 and hence the magnetic strength in the core 19 is weaker. Thespring 28 opens the armature at 24 which breaks the circuit throughpoints 21 which cuts the starting winding out of the circuit as it is nolonger needed until the next start. When the unit is connected to amotor, an initial adjustment of the spring 28 is all which is required.

It is to be noted that according to the present invention anelectromagnet semi-circular or U-shaped formation surrounds or partlysurrounds the motor shaft when mounted inside of a motor housing andthis requires less space to allow the unit to be used within existingmotor frames. There is a very limited space due to overhang of windingsand fan blades on rotor which renders any other shape impractical. Dueto the shape of this unit a magnet wire large enough for it Hi. may beused for series coil 18. This would handle split phased motors from thelowest up including 4 HP. The only requirement would be a coil spring 28suitable and in propontion to a large change in H.P., that is a springwith greater tension for the group of highest I-I.P.

As the series coil contains only twenty-five turns the 'loss ispractically zero and there is no interference.

Minor changes in shape, size and rearrangement of details coming withinthe field of invention claimed may be resorted to in actual practice, ifdesired.

We claim:

1. In a device of the character described, a circular support memberprovided with a central opening for the projection therethrough of ashaft, a plurality of spaced apart brackets connected to said supportmember, a coil connected to said brackets, wires connected to said coil,a core having its major portion arranged within said coil, a baseconnected to said core, a pair of spaced apart points extending fromsaid base, an armature having one end pivotally connected to a portionof said core, the other end of said armature being mounted for movementinto and out of engagement with another portion of the core, aninsulated strip mounted below said armature, contactors carried by saidarmature and arranged below said insulated strip, and said contactorsbeing mounted for movement into and out of engagement with said points.

2. In a device of the character described, a circular support memberprovided with a central opening for the projection therethrough of ashaft, a plurality of spaced apart brackets connected to said supportmember, a coil connected to said brackets, wires connected to said coil,a core having its major portion arranged within said coil, a baseconnected to said core, a pair of spaced apart points extending fromsaid base, an armature having one end pivotally connected to a portionof said core, the other end of said armature being mounted for movementinto and out of engagement with another portion of the 5 core, aninsulated strip mounted below said armature, contactors carried by saidarmature and arranged below said insulated strip, and said contactorsbeing mounted for movement into and out of engagement with said points,and resilient means connected to said armature.

3. In a device of the character described, a shaft, a circular supportmember provided with a central opening for the projection therethroughof said shaft whereby said support member surrounds said shaft, aplurality of spaced apart brackets connected to said support member, acoil that is wound crosswise or around a complete magnetic pathconnected to said brackets, wires connected to said coil, a core havingits major portion arranged within said coil, a base connected to saidcore, a pair of spaced apart points extending from said base, anarmature having one end pivotally connected to a pontion of said core,the other end of said armature being mounted for movement into and outof engagement with another portion of the core, an insulated stripmounted below said armature, contactors carried by said armature andarranged below said insulated strip, and said oontactors being 6 mountedfor movement into and out of engagement with said points, and resilientmeans connected to said armature, said resilient means comprising a coilspring, an ear extending from said armature and connected to one end ofthe coil spring, a securing element extending from said core, a clampconnected to the other end of the coil spring, said clamp being providedwith a slot for the projection therethrough of the securing element.

References Cited in the file of this patent UNITED STATES PATENTS458,617 Clark Sept. 1, 1891 870,139 Taylor Nov. 5, 1907 1,170,360 TaylorFeb. 1, 1916 1,907,494 Brogger May 9, 1933 2,115,597 Traver Apr. 26,1938 2,411,405 Yuhas Nov. 19, 1946 2,484,244 Pearson Oct. 11, 19492,750,537 Morris June 12, 1956

